chore: import upstream snapshot with attribution

tests/fixtures/sample.rs

@@ -0,0 +1,60 @@
+use std::collections::HashMap;
+
+struct Graph {
+    nodes: HashMap<String, Vec<String>>,
+}
+
+impl Graph {
+    fn new() -> Self {
+        Graph { nodes: HashMap::new() }
+    }
+
+    fn add_node(&mut self, id: String) {
+        self.nodes.insert(id, vec![]);
+    }
+
+    fn add_edge(&mut self, src: String, tgt: String) {
+        self.nodes.entry(src).or_default().push(tgt);
+    }
+}
+
+fn build_graph(edges: Vec<(String, String)>) -> Graph {
+    let mut g = Graph::new();
+    for (src, tgt) in edges {
+        g.add_edge(src, tgt);
+    }
+    g
+}
+
+trait Processor {
+    fn run(&self);
+}
+
+trait Logger: Processor {
+    fn log(&self);
+}
+
+struct Result<T> {
+    value: T,
+}
+
+struct DataProcessor {
+    current: Result<DataProcessor>,
+}
+
+impl Processor for DataProcessor {
+    fn run(&self) {}
+}
+
+impl DataProcessor {
+    fn build(input: DataProcessor) -> Result<DataProcessor> {
+        Result { value: input }
+    }
+}
+
+enum GraphEvent {
+    NodeAdded(Graph),
+    Processed { proc: DataProcessor },
+}
+
+struct GraphPair(Graph, Result<DataProcessor>);